JPH03236958A - Synthetic resin diffusion sheet and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a synthetic resin diffusion sheet having flexible distribution of light transmission properties generated by the increased interface easily and at low cost by laminating integrally a synthetic resin film having flexible distribution of light diffusion or transmission and a synthetic resin base blended with a light diffusion agent. CONSTITUTION:A synthetic resin film 1 having flexible distribution of light diffusion or transmission at least on one surface of a synthetic resin base 2 blended with a light diffusion agent. Synthetic resin base means a wide range from a thin sheet-shaped material recognized as a regular sheet all through a sheet of approximately 5mm thickness. As for the synthetic resin base 2 and the synthetic resin film 1 to be laminated, a film formed with acryl resin, vinyl chloride resin or thermoplastic resin such as polycarbonate resin is used, and flexible distribution of light diffusion or transmission properties means not only the distribution of transmittance based on light absorbing properties, but also the distribution based on the difference of degree of light diffusion and the distribution of combining both.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a synthetic resin diffusion material suitable for the illumination surface of a surface light source device used for internally pushed signboards, guide lights, displays, lighting equipment, liquid crystal display devices, etc. The present invention relates to a sheet and a method for manufacturing the same.

[Prior Art] Surface light source devices containing a built-in light source are widely used in push-in signboards, liquid crystal displays, lighting equipment, and the like. Such a device is generally used, which has a reflective layer on the bottom of the box, a built-in light source such as a fluorescent lamp, and a diffuser plate disposed in front. However, if the depth of such a device is sufficiently large, this is not much of a problem, but if the depth is reduced and the device is made thinner, the image of the light source, such as a fluorescent lamp, becomes visible, making it difficult for lighting equipment to have a uniform amount of light as a whole. It's hard to get caught.

In order to eliminate these drawbacks, it is possible to improve the diffusion performance of the diffuser plate, but this inevitably lowers the light transmittance and unfortunately makes the entire surface dark. be.

[Problem to be solved by the invention] In order to improve this point, recently, in a light diffusing plate made of a transparent base material mixed with a light diffusing agent, the thickness of the part where the light intensity is high has been increased. An optical unevenness removing member has been proposed (Japanese Unexamined Patent Publication No. 74004/1983).

However, changing the thickness of the light diffusing plate in accordance with the intensity of light requires setting the thickness each time depending on the shape and size of the device and the distance from the light source, which is difficult to do during manufacturing. The production cost of the mold is high and it cannot be said to be practical.

In view of this situation, the present invention has been developed by laminating and integrating a synthetic resin film with a distribution of light diffusivity or transmittance and a synthetic resin substrate containing a light diffusing agent, thereby increasing the number of interfaces and increasing the light transmission. This invention was completed based on the knowledge that synthetic resin diffusion sheets 1 to 1 with a wide distribution of properties can be manufactured easily and at low cost.

[Means for Solving the Problems] That is, the gist of the present invention is to provide a synthetic resin film having a distribution of light diffusivity or transmittance on at least the surface of a synthetic resin substrate containing a light diffusing agent. The first synthetic resin diffusion sheet is characterized by being laminated and integrated.
The second invention is a method of integrating the synthetic resin substrate and the synthetic resin film by thermal adhesion, solvent adhesion, or polymerization adhesion when laminating the synthetic resin substrate and the synthetic resin film, and further uses an acrylic resin film. The third object of the present invention is to provide a method in which the acrylic synthetic resin substrate is partially swollen or dissolved by a monomer or partial polymer that is a raw material for the acrylic resin constituting the acrylic synthetic resin substrate.

As the polymer constituting the synthetic resin substrate used in the present invention, thermoplastic resins such as acrylic resins, vinyl chloride resins, and polycarbonate resins are preferably used.

The synthetic resin substrate in the present invention contains a light diffusing agent and has a total light transmittance of 15 to 50% when formed into a sheet or plate, and a shape factor of brightness distribution of 0.6.
A sheet or plate shaped body formed from the above thermoplastic resin is preferably used.

That is, the synthetic resin substrate in the present invention broadly refers to anything from a thin plate-like body normally recognized as a sheet to a plate-like body having a thickness of about 5 mm.

As the light diffusing agent, inorganic and/or organic transparent fine particles having a refractive index different from that of the synthetic resin are preferably used.

Examples of transparent fine particles used as a light diffusing agent include inorganic fine particles such as silica, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, and calcium phosphate, or transparent fine particles made of synthetic resin. Examples include styrene and polymer beads made by copolymerizing styrene and methyl methacrylate in the presence of a crosslinking monomer.

The shape factor of the brightness distribution refers to the spread ratio of the diffuse transmitted light in the direction parallel to the sheet to the transmitted light in the direction perpendicular to the sheet in the transmitted light distribution of light incident perpendicularly to the sheet.

When the shape factor of the luminance distribution of the synthetic resin substrate is 0.6 or more, at least one synthetic resin film having a distribution of light diffusivity or transmittance is laminated on at least one surface of the substrate. When the total light transmittance is 15 to 50%, the boundary between the dark and bright areas of the luminance distribution becomes unclear regardless of the viewing direction, making it suitable for use as an illumination surface of a surface light source device. Become. The diffusion sheet obtained in this case has a transmittance of 11% and 'r2% in high transmittance areas and a low transmittance area, respectively; assuming that the reflectance is 11% and 82%, the light absorbing component is If not, it can be approximately expressed as ``, +R, +R2 + 100%.

Therefore, when T,≦R,,T2≦R2,
The unevenness of the reflectance distribution is smaller than the unevenness of the transmittance distribution.
Therefore, it has the effect that undesirable unevenness is not noticeable when the light source is turned off, when the light diffusing agent is applied, or when printing, and the object of the present invention can be suitably achieved.

Examples of the acrylic resin used as a polymer constituting such a synthetic resin substrate include a methyl methacrylate resin sheet, but methyl methacrylate alone or 50% by weight or more of methyl methacrylate and other copolymerizable monoethylenically unsaturated compounds can be used. and/or a sheet or plate-like body made of a copolymer with a polyfunctional compound. Examples of monoethylenically unsaturated compounds include methacrylic esters, acrylic esters, styrene, etc., and examples of polyfunctional compounds include glycol dimethacrylate, diallyl methacrylate-1, and trimethylolpropane. Examples include methacrylic acid esters such as trimethacrylate and neopentyl glycol methacrylate.

In addition, vinyl chloride-based resins include vinyl chloride homopolymers with a degree of polymerization of 450 to 2,500, preferably 700 to 1,100, and vinyl chloride containing 80% by weight or more of vinyl chloride and other polymers. Copolymers with monomers such as vinyl acetate, ethylene or propylene, or mixtures thereof, may be exemplified.

Further, the polycarbonate resin may be any polymer having a carbonate ester bond in its molecular chain, and specific examples thereof include aliphatic polycarbonate, aromatic polycarbonate, and aliphatic aromatic polycarbonate.

If necessary, these resins may contain compounding agents known per se, such as ultraviolet absorbers, colorants, heat stabilizers, plasticizers, polymerization degree regulators, stripping agents, and hardening agents, to the extent that they do not impair the purpose of the present invention. A fuel agent, an antistatic agent, etc. can be added. In any case, even when these arbitrary compounding agents are added, the molded sheet or plate-like body has a total light transmittance of 15 to 50% and a shape factor of luminance distribution of 0.
If it is 6 or more, the object of the present invention can be suitably achieved.

In addition, the synthetic resin film used in the present invention and laminated with the synthetic resin substrate includes acrylic resin,
Examples include films molded from thermoplastic synthetic resins such as vinyl chloride resin or polycarbonate resin.
In particular, transparent films are preferably used. An important feature of the present invention is that a light diffusing layer having a distribution of light diffusivity or transmittance is formed on at least one surface of the synthetic resin film.

Providing a distribution of light diffusivity or transmittance means not only a distribution of transmittance due to light absorption, but also a distribution due to differences in the degree of light diffusivity, and a distribution using both. Specifically, the light diffusing layer is formed by partially dyeing a light absorbing agent made of carbon, metal powder, or inorganic or organic dye and pigment, or a light diffusing agent made of inorganic or organic transparent fine particles. However, it is more preferable to apply a paint containing fine particles such as a light diffusing agent such as titanium oxide, magnesium oxide, or barium sulfate to a desired location on one or both sides of the film. It is preferable that the film be formed by coating or printing by screen printing, gravure printing, or the like. At this time, as the paint vehicle, acrylic, vinyl chloride, vinyl acetate, urethane and epoxy paints are preferably used. In this way, by forming a light diffusing layer by coating or printing, it is possible to form a light diffusing layer with variations in light diffusivity or transmittance at any location on one or both sides of the film. Become.

The acrylic resin film, which is a preferable example of such a synthetic resin film, is a polymer containing an alkyl methacrylate as a main component, such as a polymer obtained by independently polymerizing megyl methacrylate, ethyl methacrylate, butyl methacrylate, or propyl methacrylate, or one of these. Examples include films made of polymers obtained by copolymerizing two or more. It may also be made of a polymer copolymerized by adding other copolymer components such as acrylate, vinyl acetate, vinyl chloride, styrene, acrylonitrile, methacrylonitrile, etc., if necessary. Polymerization is carried out by a method known per se, such as bulk polymerization, and if necessary, UV absorbers, colorants, heat stabilizers, plasticizers, polymerization degree regulators, release agents, antistatic agents, etc. are added. Known compounding agents can be added.

Films formed from vinyl chloride resins include not only vinyl chloride dipolymer, but also 80% by weight or more of vinyl chloride and other monomers, such as vinyl acetate,
Examples include films made of copolymers with vinylidene chloride, acrylic esters, acrylonitrile, ethylene, propylene, etc.; however, metal salts of stearic acid, 2-boxy-based or tin-based stabilizers are blended during molding. Furthermore, a soft film containing a plasticizer such as a phthalate compound such as dioctyl phthalate, dibutyl phthalate, or diallyl phthalate or a phosphate ester compound such as tricresyl phosphate or trioctyl phosphate, or a plasticizer may be used. Do not add any agent at all, or
Alternatively, it can also be made into a hard film containing a small amount. In addition, known compounding agents such as pigments, fillers, ultraviolet absorbers, and antistatic agents may be added as required.

Further, as the film molded from polycarbonate resin, the same type of polycarbonate resin as used for the substrate described above is used.

The thickness of these synthetic resin films is not particularly limited, but it is usually preferably about 50 to 150μ, and many combinations are possible depending on the type of resin used as the substrate, but both If both are made of the same resin, a diffusion sheet with the best adhesion will be provided.

In the present invention, a synthetic resin substrate containing a light diffusing agent,
In order to laminate and integrate synthetic resin films having a distribution of light diffusivity or transmittance, it is preferable that the two be thermally bonded, solvent bonded, or polymerized.

The heat bonding method involves pressing and integrating the two materials at a temperature higher than their softening points. When using this method, it is preferable to select materials whose melting points or softening points are close to each other.

Solvent bonding involves bonding and integrating the synthetic resin film onto a synthetic resin substrate using the film's solvent. For example, a film made of acrylic resin is laminated with polycarbonate or vinyl chloride resin plates. When integrating, it is preferable to use a solvent such as methylene dichloride or ethylene dichloride.

Furthermore, as a method of polymerization bonding, a polymerization bonding method in which a polymerization initiator that initiates radical polymerization by heat or light is added to the monomer or partial polymer that is the raw material for either the synthetic resin film or the synthetic resin substrate. By interposing an agent between the two and performing heating or light irradiation, both are laminated and integrated simultaneously with polymerization. At this time, the polymer adhesive can be interposed between the two by any method such as coating or injection, and if necessary, a known method can be used to remove the adhesive before polymerization so that no air remains at the laminated interface. Foaming means may be applied as appropriate.

This method is particularly suitable when the resin constituting the film and/or the substrate is an acrylic resin,
In this case, the polymerization initiators that initiate radical polymerization by heat include azobis compounds such as azobisisobuturonitrile and azobisdimethylvaleronitrile, and peroxide compounds such as lauryl peroxide and pendyl peroxide. Examples of polymerization initiators that can be used and initiate radical polymerization by light include ace1 to phenones 5, benzophenones, Michler ketones, benzyl,
Benzoin, benzoin ethers, benzyl methyl ketal, benzoin benzoate, α-aziroxime esters, thioxanthone, etc. can be used.

In addition, when bonding using a polymer adhesive, the adhesive
A sensitizer, an ultraviolet absorber, a coloring agent, a light diffusing agent, etc. can also be added as necessary.

A general method for manufacturing the diffusion sheet of the present invention is to laminate and integrate a pre-formed synthetic resin substrate and a synthetic resin film by the method described above.
In a diffusion sheet whose substrate is made of acrylic resin, a casting polymerization method can also be applied. That is, a plate-shaped or belt-shaped mold made of metal such as stainless steel, aluminum, or brass, or synthetic resin such as polypropylene, polyester, detrafluoroethylene resin, or silicone resin is made in advance by predetermined printing or the like to make it transparent to light. Attach a synthetic resin film with distribution. This film may be attached directly or after applying a thin layer of tel polymer or partial polymer, which is the raw material of the acrylic resin plate or the same composition, to the mold surface. .

Paste the synthetic resin film in this way; construct the mold using a conventional method using one or more single-digit molds, and seal the periphery with a gasket in the case of a mold consisting of a pair of 1p7 plates.
In a mold consisting of an endless belt, both ends are sealed with a set of gaskets running in the same direction as the belt, and acrylic resin monomer or partial polymer added with a radical polymerization initiator is supplied to this mold. .

Then, the first stage polymerization is carried out by heating the mold to a temperature of 40 to 100°C, followed by the second stage polymerization at 100 to 150°C to complete the polymerization. The injected monomer or partial polymer partially swells or dissolves the synthetic resin film pasted on the mold surface during the polymerization and curing process.

Therefore, when the sheet is removed from the mold after completion of polymerization, a synthetic resin diffusion sheet with a tightly integrated synthetic resin film is obtained.

In FIG. 1 showing an example of the laminated structure of the diffusion sheet of the present invention, (a) shows that the inner surface of the synthetic resin film (1), which is laminated and integrated on one side of the synthetic resin substrate (2), has a light diffusing property or This figure represents a diffusion sheet on which a light diffusion layer (3) is formed to provide a distribution of transmittance. The film (11) can be formed not only on one side of the substrate but also on both sides, and the light diffusion layer (3) can also be formed not only on the inner surface of the film (1), but also on both sides of the substrate.
fb) which can also be formed on the outside or both sides.

Furthermore, a display layer (4) can be formed on at least one surface of the film (1) for the purpose of advertising or display, and in this case, the light diffusion layer (3) can be formed on either the inner or outer surface of the display layer. Moyoi fc).

FIG. 2 is a perspective view showing an example of the pattern of the light diffusion layer, and any pattern such as a linear (fa) or annular (b) pattern in which the area near the light source is dark and becomes lighter as it gets farther away, can be used. is formed. For example, the linear blurred shading pattern functions as a light diffusion layer when a straight tube-shaped fluorescent lamp is used, and the ring-shaped blurred shading pattern functions as a light diffusion layer when a ring-shaped fluorescent lamp is used. When viewed from the outside, the light source is not visible and a uniform illuminator is obtained as a whole, and even when the light is turned off, the coating of the light diffusing agent or uneven printing is completely unnoticeable. Become.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

Note that the evaluation items in this example were measured as follows.

-Total light transmittance--Performed in accordance with JIS K 7105.

・Total light reflectance...- Same as above ・Glossiness...- Same as above ・Area brightness... Guidance light equipment technical standard JIL 550
This was carried out in accordance with 2.

Reference Example A transparent copolymer film consisting of 60% by weight of methyl methacrylate, 39% by weight of butyl acrylate, and 1% by weight of 9 2-(5-methyl-2-hydroxyphenyl)benzotriazole as an ultraviolet absorber (
Gravure printing was carried out on a 74μ thick sheet using white ink containing titanium oxide fine particles as the main component to form a straight or ring-like shape with a dark center and a dark side on the sides as shown in Figures 2(a) and (b). A blurred pattern was printed so that it gradually became lighter. When the total light transmittance of the obtained film in the XY cross section was measured, the results shown in Section 3 (a) and fb) were obtained.

Example 1 The acrylic resin film obtained in the above reference example was coated on a 2 mm thick plate formed from a polyvinyl chloride polymer (degree of polymerization: 700 to 500), and 1 to 70% by weight of methyl methacrylate, "Acrivet" (acrylic resin molding material manufactured by Mitsubishi Rayon Co., Ltd.) was laminated with a photopolymerizable adhesive consisting of 30% by weight, and then an ultraviolet fluorescent lamp (20W, 4
A diffusion sheet was manufactured by polymerization adhesion by spraying at a distance of about ]Ocm for about 30 minutes.

0 Example 2 Polycarbonate resin plate (manufactured by Mitsubishi Rayon, 2mm thick)
The acrylic resin film obtained in the reference example was placed on the vinyl chloride resin plate used in Example 1, and
Overlaid between mirror-polished metal plates, the temperature of the metal plates is 1.
Heat pressing was performed under the conditions of 80° C. and a press pressure of 12 kg/cm 2 to produce diffusion sheets 1-1.

The flame retardancy of the thus obtained diffusion sheet using polycarbonate resin and vinyl chloride resin as a substrate was evaluated.

The test method was based on LJIS 550:11-19881 test method C for flame resistance of synthetic resin parts such as shells, members, and materials of the guide light equipment technical standards of the Japan Lighting Industry Association standard, as shown below.

A test piece with a thickness of 2 mm, a length of 125 mm, and a width of 12.5 mm was prepared and held with the long axis horizontal and the short axis tilted at 45 degrees from the horizontal. Marked lines were placed at 25 mm and 100 mm from the free end. put. Apply the center of the 25 mm high blue 1 flame of a Bunsen burner with an inner diameter of 9.5 mm and a length of 100 mm to the lower end of the tip of the test piece and leave it there for 30 seconds. Burning speed of 25mm and 100mm is 3/min
Those with a diameter of 8 mm or less (including those whose flame goes out midway through) are called flame-retardant abrasives.

Example 3 Methyl methacrylate monomers were prepolymerized to produce a methyl methacrylate partial polymer containing about 20% by weight of methyl methacrylate monomers. To this, 0.05% by weight of azobisisobutyronitrile, 0001% by weight of dioctyl sulfosuccinate sodium salt as a stripping agent, and 0.005% by weight of 2-(5-methyl-2-hydroxyphenyl)benzotriazole as a UV absorber. Add and dissolve 3.0% of polystyrene particles as a dispersing agent.
7-0.14% by weight of titanium dioxide fine particles were added and dispersed.

Next, a pair of molds were prepared in which the acrylic resin film obtained in Reference Example L was previously attached to one metal mold surface using methyl methacrylate, and the mixture described in -1- was injected between the molds, and the mixture was polymerized. The periphery was clamped so that the remaining thickness was 2 mm. Then, according to the conventional method of cast polymerization, 60℃
The first stage polymerization was carried out by soaking in hot water for 2 hours, followed by immersion in warm water for 12 hours.
The polymerization was completed by staying in warm air at 0°C for 2 hours to perform the second stage polymerization. After cooling it to room temperature, it was taken out from the mold into the acrylic resin diffusion sheet 1. ,
The acrylic resin film with a distribution of light transmittance was laminated and integrated, making it a good product.

Evaluation of the optical properties of the obtained sheet (Fig. 2 fa) X-Y
When measured at a location corresponding to the cross section, results as shown in FIG. 4 were obtained, and it was confirmed that the requirements were met.

Example 4 A methyl methacrylate partial polymer containing about 20% of methyl methacrylate 1 monomer was added with 1.0% by weight of magnesium carbonate fine particles, 1.5% by weight of aluminum hydroxide fine particles, and 0 titanium oxide fine particles as a light diffusing agent 3. ．．
After adding 15% by weight and well dispersing, add 0.05% by weight of azobisisobutyronitrile as a polymerization initiator and 0.05% of 2-(5-methyl-2-hydroxyphenyl)benzotriazole as an ultraviolet absorber. % by weight, 0.0% of dioctyl sulfosuccinate sodium salt as a mold release agent.
001% by weight was mixed and dissolved.

This mixed solution was poured into molds (however, a pair of regular molds) in the same manner as in Example 3 above, and was polymerized and cured to a thickness of 2 m.
An acrylic resin sheet of m was obtained.

Next, the acrylic resin film obtained in the above reference example was attached to an acrylic resin sheet via a photopolymerizable adhesive, and irradiated with four 20W fluorescent lamps at a distance of about 10 cm for about 30 minutes. Polymerization was carried out.

The composition of the adhesive used was as follows.

4. A methyl methacrylate partial polymer containing about 20% by weight of methyl methacrylate polymer was prepared, and this was heated to 97% by weight.
5% by weight, and further 2.49% by weight of trimethylbenzoyldiphenylphosphine oquinide as a photopolymerization initiator.
, a photopolymerizable adhesive containing 0.01% by weight of 2(5-methyl-2-hydroxyphenyl)benzo-1-lyazole as an ultraviolet absorber.

The acrylic resin diffusion sheet obtained as described above was good in that the film and sheet were closely integrated, as in Example 3 above.

Example 5 A methyl methacrylate partial polymer containing about 20% by weight of a methyl methacrylate polymer was added with 1.0% by weight of magnesium hydroxide fine particles, i and o weight% of aluminum hydroxide fine particles, and 0% by weight of titanium oxide as a light diffusing agent. .16 overlapping parts were added, and to this was added 0.05i weight % of azobisisobutyroni I-zil as a polymerization catalyst, 0.001 weight % of dioctyl sulfosuccinate 1-lium salt as a release agent, and an ultraviolet absorber. Then, 0.005% by weight of 2-(5-methyl-2-hydroxyphenyl)benzotriazole was added and dissolved.

This mixed solution was poured into molds (however, a pair of regular molds) in the same manner as in Example 3 above, and was polymerized and hardened to a thickness of 2 m.
m sheets were obtained.

Next, using the acrylic resin film obtained in the above reference example, a film was prepared in which a display layer was formed by screen printing on the surface opposite to the surface printed with white ink.

Then, with the display side of this film facing up, the film and sheet were sandwiched between two mirror-polished metal plates, and the metal plates were heated and pressed at a temperature of 180'C1 and a pressure of 12 kg/cm2 to form a laminate. It became.

The obtained acrylic resin diffusion sheet was good in that both were in close contact with each other.

[Production of surface light source box] The acrylic resin diffusion sheet obtained in Example 3 above was
Attached to the surface light source box shown in Figures 5 and 6,
When the surface brightness 6 in the X-Y cross section was measured, the results shown in FIG. 7 were obtained, and it was found that the example of the present invention was even better.

In Figures 5 and 6, (A) is an acrylic resin diffusion sheet, (13) is a side plate and bottom plate with reflective layers on the inner surface, and fc) is a fluorescent lamp with a diameter of 28 mm (20 W). Assembled according to the dimensions. In the comparative example, a similar apparatus was used, and a sheet made only of the diffusion resin used in Example 3 (without the acrylic resin film) was used.

[Advantageous Effects of the Invention 1] According to the present invention, a synthetic resin film having a distribution of light transmission characteristics, that is, light diffusivity or transmittance, and a synthetic resin substrate containing a light diffusing agent are laminated and integrated. Therefore, when this is used as a surface light source device with a built-in light source, the sheet thickness is uniform, but the illumination emitted from the light source is diffused, making it difficult to see light sources such as fluorescent lights when viewed from the outside. This diffusion sheet can provide uniform illumination as a whole, without the manufacturing difficulties of conventional light diffusion plates, and can be manufactured at an extremely low cost. When using acrylic resin as a material, the manufacturing method of the diffusion sheet becomes more varied, and
When vinyl chloride resin or polycarbonate is used, a diffusion sheet with extremely high flame retardancy can be obtained, and the sheet can be suitably used as a constituent material for a surface light source device having an internal heat source.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the laminated structure of the diffusion sheet of the present invention, FIG. 2 is a perspective view showing an example of forming the pattern of the light diffusion layer, and FIG. 3 is the pattern shown in FIG. 2. XY, X'-Y
Figure 4 is a graph showing the optical properties of the sheet obtained in the example. Figures 5 and 6 are graphs showing the total light transmittance in the cross section. A perspective view and a sectional view showing a state in which the invention is applied to a light source box. FIG. 7 is a graph showing surface brightness in the X-Y cross section of the surface light source box shown in FIG.

Claims (7)

[Claims] (1) A synthetic resin diffusion sheet characterized in that a synthetic resin film with a distribution of light diffusivity or transmittance is laminated and integrated on at least one surface of a synthetic resin substrate containing a light diffusing agent. (2) The synthetic resin substrate is selected from the group consisting of acrylic resin, vinyl chloride resin, and polycarbonate resin, has a total light transmittance of 15 to 50%, and has a brightness distribution shape factor of 0.6 or more. A synthetic resin diffusion sheet according to claim (1). (3) The synthetic resin diffusion sheet according to claim 1 or 2, wherein the synthetic resin substrate contains inorganic and/or organic transparent fine particles having a different refractive index from the synthetic resin. (4) Claim (1), (2) or (4) wherein the synthetic resin film is a transparent film or a transparent diffusion film formed of a polymer selected from the group consisting of acrylic resin, vinyl chloride resin, and polycarbonate resin. 3) Synthetic resin diffusion sheet as described. (5) A claim in which the synthetic resin film has a distribution of light diffusivity or transmittance by coating or printing a paint containing a light diffusing agent on part or all of one or both sides thereof. The synthetic resin diffusion sheet described in item (1), (2), (3) or (4). (6) When laminating a synthetic resin film with a distribution of light diffusivity or transparency on a synthetic resin substrate containing a light diffusing agent, the two are integrated by thermal adhesion, solvent adhesion, or polymer adhesion. A method for producing a synthetic resin diffusion sheet characterized by: (7) Acrylic synthetic resin substrate containing light diffusing agent,
When laminating an acrylic resin film with a distribution of light diffusion or transparency, the acrylic resin film is layered with a monomer or partial polymer that is a raw material for the acrylic resin that makes up the acrylic synthetic resin substrate. A method for producing a synthetic resin diffusion sheet characterized by partially swelling or dissolving it and integrating it.